This invention relates to a cable splice for an electrical cable and to a method for making a cable splice. More particularly, this invention relates to a cable splice for use in high temperature, high pressure gassy oil wells adapted to prevent depressurization-caused rupture failures and to avoid corrosion and destruction of the conductors by sulfide gases, and to a method for making said cable splices.
In general, cable structures employed for oil well service have stranded metallic conductors, usually formed of copper, separately insulated with a material of high dielectric strength, cabled and surrounded by an outer armor. In joining cable sections, a splice is formed between the conductors comprising a metallic member frictionally engaging the conductors which is insulated by a section of insulant surrounding any remaining exposed areas of the conductors and the metallic member. The section of insulant typically is formed by a plurality of layers of insulating tape, which may be further protected and confined by a heat shrinkable sleeve positioned over the splice insulation and extending over the adjacent insulation to seal the splice area.
Where the well cable is to be employed in highly gassy wells containing corrosive gases, particularly sulfides, invasion of the cable structure by low molecular weight hydrocarbons and corrosive well fluids under high pressure occurs either by way of pinholes or other defects in the primary insulation of the cable or by gas permeation.
When the cable is removed from the well bore, the external pressure is decreased, creating an unbalanced high pressure condition within the splice structure which leads to blow-out or rupture failure. Further, the conductors are particularly susceptible to attack and corrosion by the sulfides, which results in destruction of the conductors and a shortened cable life.
One method for preventing sulfide attack on the conductors has been the coating of the conductor with a sulfide-impervious layer such as metallic lead, a lead-tin alloy, or tin. The coating acts as a barrier to prevent contact of the sulfide-containing fluids with the conductor.
A method for forming a cable splice between conductors coated with lead, lead-tin alloy or tin is needed which would prevent contact of the conductors in the splice area by corrosive well-fluids and which could be carried out rapidly under field conditions.